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Leptospermum - Growing Guide
The leptospermum which we grow in the nursery are reasonably hardy. Nearly all are named forms of Leptospermum scoparium, the ‘Manuka’ or ‘New Zealand Tea Tree’. They thrive in the West Country and are generally very easy to grow outside in the right conditions.
Will they tolerate a few degrees of frost from time to time? Yes, certainly, but only in the right situation. We know of a large south facing upraised border in Kent which grows nothing but leptospermums. They have hardened off and acclimatised. In effect they have adapted to a harsher environment and grow in a much more prostrate or dwarf fashion than in the milder western counties.
Will leptospermum be killed in a very severe cold winter? Probably but, again, if their positioning and location is chosen with care, they have a fair chance of surviving.
Further north leptospermums are perhaps best handled as patio plants in containers and brought back into the greenhouse or conservatory for the winter. Alternatively they can very well and successfully be grown in either all year round. Water sparingly in the greenhouse and feed well for the rest of the year with liquid fertiliser once a month while the plant is putting on new growth.
Leptospermums readily grow in Cornwall to 10-12ft high (obviously the dwarf and prostrate forms do not). In colder counties they may only achieve half this size.
However they demand hot, dry and well sheltered situations. Up against a sheltered south or west facing wall or bank is perfect.
The soil need not be particularly fertile or good. In the wild in New Zealand it generally is not! Thinner coastal (ericaceous) soils are ideal.
It is wind chill rather than frost which can often kill leptospermums outside milder western counties. Sloping ground which does not freeze is another plus. Waterlogged wet areas are a disaster.
Aside from cold issues, leptospermum are very easy to grow, grow exponentially, and flower profusely over a lengthy period between April and June.
The flowers are in clusters of two or three with five broad ovate petals.
The flower colour range from white to pink and red and there are varieties with both single and double flowers. The odd flower is often observed in the winter months as well which betrays where Leptospermum scoparium comes from.
The foliage is needle like and some forms have attractive reddish or dark green new growth. Others have light green new growth set against a darker green background.
The popularity of this slightly delicate plant (which is currently considerable) is down to its ability to make a great flowering spectacle in the garden or greenhouse.
If you are worried about the risks of a cold winter leptospermums are very easy to propagate.
Semi hardened or ripe new growth cuttings will root very quickly in summer with some bottom heat. We take cuttings each year from plants in the nursery and they are large enough to be saleable in 2 or 3L pots in 18 months.
The seeds, which are large and swell quickly at the centre of the flower, can be sown in spring or autumn but some bottom heat is helpful. Older leptospermums often have copious old brown seedheads lower down the stem from previous years’ flowers. These older seeds are usually still fertile.
Three exceptional Leptospermum's we recommend
Three exceptional leptospermum varieties which we recommend:
Leptospermum ‘Nicholsii’ – carmine red flowers and dark purplish-bronze foliage. First raised in 1904 but still popular and proven to be hardier than most varieties.
Leptospermum ‘Red Damask’ – huge double, long lasting, deep red flowers which was bred in California 70 years ago. Again it has lasted the test of time.
Leptospermum ‘Snow Flurry’ – double white flowers in profusion.
If you prefer a pink single or double variety please study our website for more